1. Field of the Invention
This invention generally relates to a light filament and a method for making the same, and more particularly to a light filament and a method for making the same formed of carbon nanotubes. The instant application relates to the copending applications Ser. Nos. 10/334,547 filed Dec. 31, 2002 and 10/335,283 filed on Dec. 31, 2002.
2. Description of the Related Art
Electric light filaments are typically made of materials which are either polycrystalline in nature or which are amorphous, or noncrystalline, in nature. Such materials become brittle when they are subjected to high temperatures for prolonged periods.
Polycrystalline materials, which include the majority of commercially available metallic filaments, are characterized by the presence of crystal grain boundaries, dislocations, voids and various other microstructural imperfections. These microstructural imperfections lead to grain growth and recrystallization, particularly at elevated temperatures, which in turn lead to increased brittleness and diminished strength.
Metallic filaments have relatively low electrical resistivity. Therefore, they are often made quite long and are tightly coiled in order to fit within a light bulb of suitable size. Coiling of a filament reduces its effective radiating surface area because parts of the coiled filaments partially block other parts, thereby diminishing the radiative efficiency of the filament. This results in a coiled filament's higher electrical power consumption to produce the same amount of radiating surface area. A light filament having a higher surface area to volume ratio can provide greater radiative efficiency.
Hence, an improved light filament that overcomes the aforementioned problems is desired.